Method of and apparatus for balancing aircraft.



- J.P.TARBOX.

. METHOD OF AND APPARATUS FOR BALANCING AIRCRAFT.

APPLICATION FILED AUG-l5, 1 912.

- 5 SHEETS-SHEET I.

Patented Oct. 17,1916. '7

J. P; TARBOXL. METHOD OF AND APPAR'ATUSfOR-BALANCING A IRCR AfT APPLICATION man Au e.1s,- 1912.

1,201,648. "Patented Oct.17,1916.

5 snasrsesmzu 2.

I. P. TARBOX.

METHOD OF AND APPARATUS FOR BALANCING AIRCRAFT.

APPLICATION FlL-ED A. lG.l5,. m2

1,201,648. Patented. Oct. 17,1916.

5 SHEETSS.HE ET 3- wi/iwvemo 1.P. ARB0x. I METHOD OF AND APPARATUS FOR BALANCING AIRCRAFT.

A;P.PL |CATION FILED AUGASVIQVIZ. 1,201, 48.

Patented 0m. 17,1916.

5 SHEETS SHEET 4,.

J. P. TARBOX. METHOD O-F ANfD APPARATUS FOR BALANCING AIRCRAFT.

APPLlCATlQN FILED AUG.I5I 19l2.

Patented Oct/17,1916.

5 SHEETS-SHEET 5.

' balancing devices JOHN P. TARBOX, on wAsHIneron, nrsriarci: on COLUMBIA.

. METHOD OF AND APPARATUS FOR BALANCING AIRCRAFT. I

neoaeas Specification of Letters Patent.

Application filed Aug'iistl5, 1912. Serial No. 715,27

To all whom it may concern:

Be it known that 1, JOHN P. TARBOX, a citizen of the United States,,residing at Washington, District of Columbia, have invented a new and useful Improvement in Methods of and Apparatus for Balancing Aircraft, of which the following is a specification. w

- My invention consists of a balancing mechanism of the servo-motortype, in which there is provided a source of power, power transmitting means, operating means for associated therewith, power controlling means controlling the application of power to said operating means, a standard of position governing said con: trolling means and determining the operation of the balancing devices thereby, and what is commonly known as a follow-up connection between the controlling means and the operative means for the balancing devices.

Specifically, my invention has particularly to do with such a mechanism which will establish a checking force as the air-craft approaches normal fromany position of un-' balancing whereby the momentum of the craft is checked, and it is stopped precisely' at normal without rocking or oscillation. My co-pending application Serial No. 715,276 filed August 15, 1912, has to do with a method ofbalancing the air-craft according towhich such a checking force is setup.

My present invention also includes a method according to which a checking .forceis set up, which method I shall clai'm herein,

the method of the presentinvention being a specific improvement over and above the method of the application referred to.

By reference to Figure 1 of the sheets .of drawings presented herewith, the diflerence between the two methods will be clear. The full line curve, Roman numeral I, is the curve 'showlng the excursion of the air-craft during unbalancing, while the dotted line curve, Roman numeral II, shows the excursion of the balancing devices in opposition, to the-unbalaneing. The balancing devices, move outwardly with the craft to a position of maximum deflection a, proportionately to the unbalancing of the craft. Upon the ensuing-response of the craft to the-corrective force set up, the balancing devices are moved back-to normal before the craft reaches normal, and thereupon moved past normal in the opposite direction to set up the checking force which damps the momentum of the craft as itapproachesnormal. In my co-pending application referred to,

the method of my invention includes the sudden returning of the balancing devices to normal after the checking force has been set up, by a practically instantaneous movement,- the maximum checking force being reached as the craft comes to a halt at normal. This is shown by the dot and dash extension 0. According to the present method, however, the maximum checking force is reachedjust before the craft halts at normal position, and it is gradually. de creased, (of course, in a very small interval of time) as the craft comes to a halt at normal. Thus, according to the present method the curve of the checking force approximates in shape an isosceles triangle, while according to the other method, the curve approximates a right-angle triangle with the rightangle at the normal position of the craft.

The method of the present invention is practiced by the use of a follow-up connection in, the servo-motor mechanism above described, which follow-up connection is constituted by a reversible fast-forward and slow-return movement. By this means, the controlling means or the standard of position, as the case may be, is given a follow-up Patented @et. 17, rare.

movement during the forward movement of the balancing devices proportionately greater than the follow-up movement on the the return movement they are moved past normal to establish the checking force. At or near the cut-off point, a shifting of the controlling means or standard of position is accomplished, whereby the return of the balancing, devices takes place with the craft to normal.

, One embodiment of my invention is shown in the accompanying drawings, in which Fig, 1, previously mentioned, is a diagram showing the curves of the craft and balanc ing devices respectively during excursions Uofunbalancing, Fig. 2 is a diagrammatic sectional view of the-mechanism of my in ventionwhen the craft is in normal position; Fig. 3 is a similar view showing the positions ofthe parts when the craft is in ;an extreme position of unbalancing, Fig. 4 is a similar view showing the positions of the y parts after response has ensued, and 111st as the balancing devices reach normal and-are in the act of passing normal to set up the checking force, Fig. 5-1s a sim lar view showing the positions of theparts the instant the maximum checking force has been 'set up,

the balancing devices having reached their maximum reverse position, and the reversev movement of the controlling means or standard of position having been accomplished to '20 start the balancing devices back to normal, and Fig. 6 1s an end elevation showing the arrangement of the follow-up connection with respect to the remainder of the mech anism.

- 5 Referring first toFig s. 2 and 6, it will be seen that I have illustrated-my invention in connection with a fluid-pressure servo-motor. This motor comprises a source of power in the form' of a pump 10, and power transn1itting means in the form of a cylinder 12 and piston l3,'an operating means for balancing. devices in the form of an extended piston rod 14, controlling means in the form of the valve 15 for controlling the transmis- U sion of power to the operating means 14,

and astandard of position 16 in the form of" a pendulum pivoted on a lever 17 and operatively connected with valve 15.

The lever 17 constitutes apart of the fol low' up connection. At its lower end 18 it is pivoted intermediate the ends of a lever 19 which in 'turn is connected at its lower end 20 to the normally fixed cord 21 which is connected with" the steering-gear 22 for .45 operating" the vertical rudder 23 of the craft. Whenever the vertical rudder 23 is shifted to cause the craft to turn right or left the lever'19 is shifted, resulting in a shifting of the standard 16, all as fully set forth inmy co-pending application Serial No. 607,736

filed February 10, 191.1. This action of itself forms no part. of my. present invention. The upper end of lever 17- is connected' by a pm and slot connection 24 with the piston rod '14, whereby whenever the balancing devices are moved the lever 17 is shifted toshift the pivot of the-pendulum 1-6 and effect through the pendulum the cut off of-the supply of-power bv the valve 15.

This is the usual follow-up action. a The upper end of'lever 19 on which lever 17 is pivoted, is adjustably connected to disk 25 rotatableon a fixed shaft 26 by means of a link 27 pivotally connected to block. 28

which may be fixed in any position in slot 29 in the disk 25. I The normal position of the disk 25 is such that the connection -28 29 is'on a normal line NN perpendicular to the piston rod 14. The disk 25 is provided with a concentric segment 30, nor- 7o mally symmetrically disposed with reference to the line NN. The disk and segment are biased to this normal position by the opposed springs 3131, or the equivalent, being otherwise free to turn a limited distance around the fixed shaft 26. Also freely journaled on the shaft 26 is an upwardly extending lever '32 normally on line N N, but connected by pin and. slot connection 33 with the piston rod 14 which operates the balg0 ancingdevices. Concentric with the segment 30, and having an upper face 'coin ciding with the upper face of the segment 30 is a fixed segment 34 located immediately behind the segment 30. Each of these seg- 35 ments is provided with a notch, 35 in the movable segment 30 and 36 in the fixed seg ment 34, the notches normally coinciding on the line NN. Normally engagingin the [notches 35-36 is tooth 37 controlling the position of the oppositely pointed pawls 3838" which are biased to the normally disengaged position shownby means of the fiat spring connecting their pivot 39 with a fixed pin 40 on the lever 32 on which the .95

pawls are pivoted. The pawls 38-38' are not precisely in line with each other longitudinally, being displaced in order to independently engage the laterally displaced lugs 41-41 on the surface of the movable seg- .100 ment 30;

On the under side of the disk 25 connected with the segment 30 are provided a pair of oppositely disposed sets of ratchet-teeth 4242. A normally fixed transverse shaft 43 below and parallel to'sliaft 26 carries a pair of pawls 44'44. adapted to be brought into engagement with the ratchets 4242.

a pair of brackets 52 depending from the 12pshaft 26 and shiftable by means .of lever-53 whenever the cord 21 of the vertical rudder 23 is shifted, whereby the shaft 43 together with the pawls, may be shifted onewway or the other around shaft 26 when'the pivot 49 ofthe pendulum 16 is shiftedby'the cord 21. Now assuming an unbalancing of the craft to the left through an angle a, the'servomotor mechanism has operated to givethe balancing devices a maximum'deflection to 3 a position a (Fig 1), with the result that the'parts take the position shown in Fig. 3.

It is "readily seenthat upon initial downward movement to theleft the pendulum 16 moves the valve 15 to the right, admitting fluid pressure by passage 15 to the right hand end I of the cylinder 12, driving the piston 13 to the left. This movement of the piston 13 it will be observed has not only carried lever 17 to the left around its pivot 18, but 'through movement of the lever 32 to the left about shaft 26 has shifted the movable segment 30 together with the disk 25 and through the link 27 shifted the lever 19 to the left and with it the pivot 18 of lever 17 -.which it carries. Thus lever 17 is given a compound movement to the left which results in the pendulum being moved to the left at a higher rate of speed, .than it would be if the pivot 18 were fixed, and the action of the follow-up connection were simple and through the connection of the lever 17 with the piston rod 14 alone. Thus the follow-up connectionimparts to the pendulum standard of position 16 a relatively greater" movement per unit of movement of the piston rod 14. And the valve 15 cuts off the supply of power to the cylinder 12 when the balancing devices have been moved through a relatively less distance than they would have been moved if the movement of the lever 17 had not been compound. The mechanism operates the balancing devices at a rate of speed suflicient'to enable them to keep pace with the unbalancing of the craft. During this operation the left hand pawl 38 engages the left hand .lug.41, by reason of the counter-clockwise tilting of the pawls 38 38 when the lever 32 is-moved to the' left with respect to the fixed segment 34, the tooth 37 having by this movement been moved to the right out of the notches 3536.

The segment 30 having been moved to theleft, the tooth 37 -is prevented from again entering notch 35 or notch 36 under the bias of spring 32, by reason of the displacement of the notches 35-1-36 from each other. The tooth 37 can only. reenter the notches and the pawls 3838 can only occupy their normal positions when the notches 35-36 CO:

v incide.

with the ratchet .42. When the, craft com-.

mences to respond, the pendulum- 16 moves to the right, commencing thereturn of the balancing devices to normal. Thus the lever 32 and pawl 38 are moved to the right away from'lug- 41, the tooth 37 riding upon the peripheries of the segments 30 and 34, but the segment 30 does not return to normal the valve 15 to the left as the left hand end of theecraft rises admitting fluid pressure to the left hand end of the cylinder 12 and moving the piston rod 14 and-attached parts with the lever 32, being held in deflected position by the pawl 44'.

As the craft responds, the return movement of the balancing devices continues until they reach normal position as shown in Fig. 4. The angle a it will'be observed is .less, the craft havingnot yet reached normal ,(see Fig. 1) though the balancing devices aforesaid have reached normal and are in'the act of passing it (see the point p F ig. 1). During this movement by reference to Fig. 4 it will be observed that the segment .30, and hence the lever 19 and'pivot 18 of lever 17 have not moved, bein in the same relative positions as respects, tie line NN that they occupied when the craft was in the position of Fig. 3. Thus lever 17 during this return movement of the balancing devices is given only a simple movement by connection-with the rod 14. The pivot "'49 of'the pendulum'16 is therefore moved at a relatively slower rate of speed than it was on the forward movement, with the result.

' that the valve 15 cutspfi later. As shown,

the balancing devices have reachedv normal, the lever 32 having reached the normal line N-N as in Fig. 1, but the valve 15 still holds open to fluid pressure the left hand 2 end of the'cylinder' 12. Thus the balancing devices are moved past normal in a reverse direction to set up a checking force in oppositionto the momentum of the craft as it approaches normal.

The position of the parts when the maximum checking force-.0 (Fig. 1) has been set up, is shown in Fig. 5. It will be observed that the lever 32, and hence the balancing. devices connected-with the operating piston? rod 14, have been moved to the right of the normalline N-lT. In this position of the balancing devices, however, something further takes place. The pivot 49 of the pendulum as shown in Fig. 4, has not yet reached its normal position, the balancing devicesbeing in Fig.4 in normal position, and the pivot having been returned toward normal at a slower rate ofspeed. Thus the shaft 43 is still tilted to the left and pawl 44 still engages ratchet 2',- Inthe movement of the balancing devices past normal, however, the pivot 49. reaches its normal position and disengages pawl 44. Whereupon the springs 3131 immediately restore the segment 30' to its normal position as shown in Fig. 5. This movement elfects both a cutoff of the supply of power to the left handend of the cylinder 12, and an admissionof powerto the right hand end of the cylinder '12, thepivot 18 of the lever 17 having been instantaneously shifted to the right through the instantaneous return movement of lever- 19 to normal with the segment 30. Immediately the return of the balancing devices to normal takes place in unison with the movement of the craft through the small remaining angle a to normal, with the result that both the balancing devices and the craft 'reach normal at the same time, and due to the establishment of the checking force and its maintenance during-this latter portion'of the return movement of the craft,

the craft stops still, precisely at the normal position. During commencing withthe parts in the position shown in Fig. 5, it will be observed that pawl 44 is in engagement with ratchet 42,

' the pivot 49 of the pendulum having been;

moved to the right of its normal pogtion, but this is Without effect, since the pawl 38 does not engage lug 41 until returned to the-right instead of to the left, the operation is the reverse of that just described, the pawl 38 engaging lug 41 and pawlf44 initially engaging ratchet 42, in the fast compound forward movement of the lever: 1], while the ensuing slower return movement is to the left, and the checking forceis, of course, set up in the opposite direction through a final left hand movement of lever 32, similar to the right hand movement shown in Fig.

5. With this operation of the mechanism in mind, it will be seen that *with a less un-- balancing movement there Wou'ldbea correspondingly less movement of the piston rod 14, and a less initial deflection of the balancing devices, with a smaller corrective force. Thus the initial corrective force set up is always proportional to the unbalanc- .ing of the craft.- So also, the checking force, being determined in each case by the maximum movement of the piston rod 14 which sets the pivot 18' of the lever 17* through the segment 34 and attached.parts,is proportional to the unbalancing of the craft. These factors are thus the same as in my copending application initially referred to.

But the checking force, instead of being suddenly removed, is gradually removed through operation of the mechanism itself The sudden return of the pivot 18 of lever 17 to its normal position, results in indirect operation of the balancing devices by the the last stage of'the operation.

mechanism instead of direct operation of the balancing devices, as in my co-pending application.

Whenever it is desired to bank the craft to make aturn, the cord 21 is operatedto shift-the lever 19 around its pivot 19 thus shifting pivot 49- of the pendulum to effect the necessary banking. During this shifting the segment 30 is held in normal position by springs 3131' and'by thepawls'3838, which engage one or the other of the lugs 4141 Whenever force. is applied to lever 27 through movement of lever 19 bycord 21. The presence of tooth 37 in notches 3536 also tends to hold the segment 30 in normal position.

It is not desirable that the symmetrical action of the fast-forward and slow-return movement of the follow-up mechanism (symmetrical as respects movementson opposite sides of their normal position) be interfered with through shifting of the pendulum-pivot 49 p effect banking as it would be if-shaft 43 were fixed, the engagement of one of the pawls 44-44 being brought about through i the ensuing movement of link 48 at the wrong time. Therefore, connection 53 with the cord 21 isprovided whereby the'shaft 43 is shifted around the shaft 26 in the same general direction as the pivot 49, and in such degree as to keep pace with it and prevent the engagement of pawls -4444 until suchtimaas the balancing devices are operatedin response to the shifting of'the pendulum pivot 49. This connection 53 may or may not be used as desired. The mechanism is operative in either case.

The embodiment of my invention which I have described is the best'form now known to me, but 'my invention is capable of many other embodiments without departing in anywise from its generic spirit Even the embodiment which I have shown, may be compacted and its elements re-arranged to secure lightness, and compactness, and to change the degreesiof movement of the several parts without 'in anywise departing from its elemental-and essential nature, All

such changes may be-most readily made by those skilled in the art, and all of them fall within the scope of my invention, and are covered by the annexed claims.

I particularly wish it understood that any fast forward and slow return movement, or any double follow-up connection of the gen eral class to which the specific movements ,disclosed belong, may be used instead of those disclosed.

over the angular position of the plane ofthe craft with respect to the horizontal plane or surface of the earth.

Claims:

1. The method of balancing anaircraft which consists in setting up a momentum checking force as the craft is returned to normal under the effect of corrective forces force bearing a uniform ratio .to the cor-.

rective force used during any vunbalancing of the craft, said checking force being gradually increased to a maximum reached in the return to normal movement of the craft when the angle between-the position of the craft at the maximum of the checking force and the normal position'of the craft is approximately one-half of the anglebetween the position of the craft at inception of the checking force and the normal position of the craft, and as the craft passes through the remaining'half of said angle into normal position, gradually decreasing the checking force from maximum to zero.

3.'The method of balancing an aircraft which consists (l) in establishing the corrective forces with the forward unbalancing of the craft progressively and substantially proportional thereto, (2) as the craft responds and returns toward normal progressively removing the corrective" force in greater proportion than it was established whereby the initial proportion between the movement of the craft and the corrective forces is destroyed andthe corrective force is entirely removed before the craft reaches normal, (3) thereupon progressively setting up a maximum checking force in the opposite direction before the craft reaches normal (4) and progressively effecting the removal of the checking force as the craft moves into normal position. I e

4.-. Anautomatic balancing system for aircraft comprising balancing devices, a power driven actuating mechanism for said balancing devices, a standard of position controlling the operation of said power driven mechanism, and means arranged to vary the relative extent of direct and reverse movements of the actuating mechanism upon unbalancing and return movements of the craft interpolated between said standard of position and said actuating mechanism and ac-;

tuated through operation of the" said actuating mechanism.

5.--Anautomatic balancing system, comprising balancing devices, a power driven actuating mechanism for said balancing de vices for imparting to said balancing devices direct and reverse movements upon movement of the craft from a determinate normal position and return thereto, a standard of positiongoverning the operation of said actuating mechanlsm, and an actuating movement'modifying device set during a direct actuating movement of said mechanism and modifying in accordance with its setting the reverse actuating movement thereof.

6. An automatic balancing system for aircraft, comprising balancing devices, a "power driven actuating mechanism for imparting to said balancing devices forward and return .movements from normal position, a standardof position arranged to governthe operation of saidactuating mechanism in accordance with the position of said craft, a

control transmitting mechanism intermediate said standard of position and saidactuating mechanism, including a diiferentially acting control movement device one element of which at a time is active in one direction of .movement of said actuating mechanism, and a multiple number of elements of which are active simultaneously in opposite direction of movement of said actuating mechanism whereby the balancing devices are actuated to different extents according to the directionsin which they are moved from or toward normal.

7. An automatic balancing system for aircraft, comprising balancing devices, a power driven actuating mechanism 'for imparting to said balancing means forward and return movements from normal posltion, a standard of position arranged to govern the operation of said actuating mechanism in ac cordance with. the position of said craft, a

control transmittingmechanism intermediate of said standard ofposition and said actuating mechanism, including a differentially acting control movement device one element of which at a time .is active in one direction or movement of said actuating mechanism, and a multiple number of elements of which are active simultaneously in opposite direction of movement of said actuating mechanism whereby the balancing devicsare actuated to diflierent extents according to the directions in which they are moved from or toward normal, and a restoring device rendered active as the craft ap proaches normal position to restore the differentially acting control elements to normal positional relation.

8. The method of balancing a craft which consists in setting up a momentum checking force as the craft is returned to normal under the effect of corrective forces and of a value bearing-a determinate ratio to the corrective force used during unbalanci'ng of the craft'according to the degree of.unbalanc- 13.0

ing, and gradually removing said, checking I force as the craft reaches normal position;

9. The system of the character described comprising balancing devices, a servo motor for operating the same, a standard of position for controlling said servo motor and differential follovv-up connections associated 10. A system of-the character described comprising a servo-motor, a standard of po? 'siti'on for controlling said 'motor and a vari able ratio follow-up mechanism associated therewith," includingmeans actuated through the initialoperation. of the servo motor to vary thera tio of transmission of the followup device. during subsequent operation thereof whereby the movement of the balancing devices to different extents is produced according to thestage of their operation. a

. JOHN P. TARBOX Witnesses: i

J AMES H. MAR-R, CHAS. S. GRAMMAN 

